Safeguarding of superheaters



Feb. 19, 1935. B BELOHLAVEK 1,992,115

SAFEGUARDING Filed May 28, 1952 P ented Feb. 19, 1935 a PATENT OFFICE I SAFEGUARDING 0F :SUPERHEATERS BrunoBlohlavek, Vitkovice, Czechoslovakia I Application May 28, 1932, Serial No. 614,213 Germany'May 29, 1931 11 Claims. (cum-4 79)" already been proposed to pass the surplus steam,

undera positive pressure generated by a pump,

through the superheater and then return it, in

circulation, into the-water space of the boiler.

I develop this method for safeguarding superheaters even in the case'of partial loads. Duringpartial loads the superheater tubes are endangered by the circumstance that the steam tube walls-. According to the invention superheaterscan be safeguarded'against' undue accumulation of heat during partial loads in that' a pump, a pipe with a control device on the intake side of the-pump is provided in parallel connectionwith the superheater. In this case, use is made of the phenomenon that the influence ofthe rise in temperature resulting from the influx of the superheated steam, in circulation, at

by the influence of the increased velocity on the conditions of heat transmission.

invention-ensures that this safeguarding is maintained .without any unfavourable reactions on other constructional or working parts, -2and in particular that there is no need to modify or affect the final superheat of the steam, which can be maintained to the full, under perfect control,

down to minimum loads. For superheaters composed of a radiant section and a contact section, there is the further advantage that heating by radiation can be most extensively employed and,

consequently, the area of heating by contact can be reduced to a minimum. V

Three embodiments of the invention as applied for example to a Ldffler boiler, are respectively illustrated by Figs. 1, 2 and 3 of the accompanying drawing.

velocity corresponding to the load on the plant is no longer sufiicient for adequately cooling the the point it enters the superheater, is outweighed The Ldiiler boiler (U. S. Patent 1,740,254) comprises, as is known, a cylindrical boiler 1 in which the evaporation is effected by the admission of superheated steam, a superheater 2 which (as indicated by the arrows) is heated from A and is preferably composed of a section heated by radiation and of a succeeding section (in the direction of the new of steam) heated by contact with the furnace gases, and a pump 3 which draws saturated steam from the boiler through a pipe 4 and forces it through the superheater 2. After being superheated a portion of the steam is led through the pipe 5 to the utilization points, and

the remainder is conducted, under the positive pressure generated in the pump 3, in circulation and as a heat carrier, through the pipe 6 back to the boiler 1.- V

[In the embodiment according to Fig. -1, the present invention provides a pipe 7' fitted with a control member 8 and passing from the pipe 6 to the intake pipe 4 of the pump 3, said pipe '7 being shunted in parallel with the superheater 2. During partial loads a portion of superheated steam, regulated by the control device 8, can be drawn by the pump 3 throughthe pipe '7 and redelivered to the superheater 2 together with saturated steam from theboiler 1. In this manner an auxiliary, positive circulatory flow is superimposecL'in the superheater 2, on the flow corresponding-to the load. V

The amount of steam taking part in the shortcircuit circulation is regulated in accordancewith the temperature of'the heated tube walls. For this purpose devices 9 are provided which supervise the temperature of'the tube walls at various pointsa'nd set the control device 8 accordingly, as is indicated by the impulse conductor 10. Y

' Fig. 2 represents a similar embodiment in which, howeven the safeguarding action is restricted to, the first, and most highly stressed sec tion of thesuperheater 2, for example the radiant-heat sectionof the latter. V n

The methods of connection according to Figs. 1 and 2 can'be combined (Figi 3) by arranging a pipe 7, on the intake side of the pump 3, in parallel connection with the superheater 2 and connecting the latter, by sections, with the pipe 7 through pipes 11 also provided with control devices 8. In this arrangement communication is also established, by means of a pipe 12 provided with a control device 13 and connected between the pipe 7 and the delivery side of the pump 3 in front of the superheater, whilst a second control device 13 is provided at the point r where the pipe '7 enters the intake pipe 4 of the pump 3. By means of the pipe 12 and the valves 13, and also by suitably setting the valves 8 in the pipes 11, a controllable amount of the steam can be drawn from individual points of the superheater 2. With this arrangement, therefore, the velocity of flow in the several sections of the superheater 2 can be modified in stages by suitable short-circuiting and by-passing.

The device according to the invention can also be applied with advantage to heating-up Loifler boilers and similar steam generators.

I claim:

1. The method of safeguarding the superheater of a steam generator system during partial loads, consisting in pumping a controllable amount of steam, after sup'erheating, directly back to that part of the superheater subjected to the greatest stress, and automatically regulating the amount of steam so short-circuited in accordance with the temperature of the superheater tube walls. 7 c j a 2. The method of safeguarding the superheater of a steam generator system during partial loads, consisting in pumping a controllable amount of steam from individual points of the superheater directly back to the superheater inlet.

3. In a steam generator system including a cuit with difierent points of'the superheater, and,

means for controlling the amount of steam drawn from the points of the superheater through said circuit and back to the superheater inlet.

5. A steam generator system comprising in combination, a boiler, a superheater having its inlet connected with the steam space of the boiler and its outlet also connectedwith the boiler to form a circuit, a superheated steamsupplymain connected with the superheater outlet, a pump in the inlet connectionto-the superheater, a pipe leading from-an intermediate point'of the superheater to the inlet side of the pump to form an auxiliary circuit, and valve means in the pipe.

6. A steam generator system comprising, in combination, a boiler, a superheater having its inlet connected with the steam space of the boiler and its outlet also connected with the boiler to form a circuit, a superheated steam supply main connected with the superheater outlet, a pump in the'inlet connection to the superheater, a pipe connecting the superheater outlet with the'inlet side of the pump, pipes leading from individual points of the superheater to said first mentioned pipe, and valve means in each of said pipes.

'7. The method of safeguarding the superheater of a steam generator system during partial loads, consisting in positively superimposing a controllable circuit of superheated steamon the flow of saturated steam through the superheater corresponding to the load, said circuit leadi ng from individual points of the superheater directly back to the superheater inlet.

8. A steam generator of the character set forth in the Ldflier Patent #1,740,254 dated December 17,1929 comprising in combination, a boiler, a superheater having its inlet connected with the steam space of the boiler and its outlet also connected with the boiler to form a circuit, a superheated steam supply main connected with the superheater outlet, a regulable pump in the inlet connecting to the superheater, a pipe leading from 'an intermediate point of the superheater to the inlet side of the pump to form an auxiliary circuit, and valve means in the pipe.

9; A steam generator system of the character set forth in the LoillenPatent #1,740,254 dated December 17, 1929 comprising incombination, a

boiler, a superheater having its inlet connected with the steam space of the boiler and its outlet also connected with the boiler .to form a circuit,

a superheated steam supply main connected with the superheater outlet,-a regulable pump in the inlet connection to the superheater,- a pipe con necting the superheater outlet with the inlet side:

of the pump, pipes, leading from individunl'points of the superheater to said first ,rnentioned pipe, and valve means in each of said pipes. l

10. In a steam generator including a boiler nd' I a superheater, particularlyot the .typeprovidBd with radiating and convection heating sm'i'aces,

means for safeguarding the said superheater, a

short circuiting conduit extendingfroman intermediate point of the superheater directly back-i70 the inlet of the superheatenfa mechanically oper ated regulable pumpdisposedin the said shortcircuiting conduit and meanslfor controlling the amount of superheated steam passing through the said circuit.

11. In a system of thecharacter describedin-. eluding a boiler and a superheater, particular yof the type provided with radiation and COIIVBC? regulable pump disposed in the said short-cir-f cuiting conduit, said pump withdrawing with small partial loads a predetermined, and regulable quantity ofsteam at the said intermediate point of the superheater and by passing the same through said conduit directly back to the superheater inlet; the quantity of steam passing through the said superheater portion being increased by this predetermined and regulable amount over that quantity'which corresponds to the load. 

